) []prometheus.Metric {
	metrics := make([]prometheus.Metric, 0, len(m.values))
	for metricName, mv := range m.values {
		desc := m.descriptors[metricName]
		promDesc := desc.toPromDesc(namePrefix, extraLabels)
		for _, v := range mv {
			// labelValues is in the same order as the variable labels in the
			// descriptor.
			labelValues := make([]string, 0, len(v.Labels))